Having initiated the approval, designed the validation studies, and provided all dissolved oxygen data used to develop the ASTM method as well as the EPA recommendation for interim approval, the Hach LDO(r) sensor is the pre-eminent instrument for measuring DO concentration in water. Water quality professionals can be confident that the Hach instruments meet all performance specifications of the approved methods.
How does it work?
1. The LDO sensor uses a sensor cap that is coated with a luminescent material. Blue light from an LED strikes the luminescent chemical on the sensor. The luminescent chemical instantly becomes excited. As the excited chemical relaxes, it releases red light. The higher the oxygen concentration, the less red light given off by the sensor cap. The red light is detected by a photo diode. The time it takes for the chemical to return to a relaxed state is measured.
2. The oxygen concentration is inversely proportional to the time it takes for the luminescent material on the sensor cap to return to a relaxed state.
3. Between flashes from the blue LED, a red LED of known intensity is flashed. The red LED acts as an internal standard for reference comparison to the red light given off by the luminescent sensor cap. This comparison allows the sensor readings to remain stable for long periods of time.
What does this mean for the user?
Unlike polarographic dissolved oxygen sensor technologies, the Hach LDO sensor does not consume oxygen. It does not require frequent calibration or cleaning, resulting in longer sensor life and more stable and accurate readings.
In addition, because the sensor is not consuming oxygen, a circulator is no longer required to maintain flow around the LDO sensor. There are no electrodes or electrolyte to consume. There is no membrane to puncture or tear. Frequent calibration is not required as the instrument continually references itself to a red LED of known intensity. All of this makes Hach LDO the most reliable and accurate Dissolved Oxygen sensor on the
The new Series 5 consists of the Hydrolab DS5X (DataSonde 5X), DS5 (DataSonde 5), and MS5 (MiniSonde 5).
Hach LDO(tm)... available only on Hydrolab Series 5 instruments!
Hach LDO integrated into the Hydrolab Series 5 instruments is the most significant breakthrough
technology for multi-parameter water quality monitoring instruments in years!
The key benefits of the Hach LDO sensor are as follows:
· Calibrations last longer than ever before without drift, so deployment length is improved
· No anode or electrolyte to consume means extremely stable measurements
· DO was the limiting factor in deployment length, so now site visits are reduced
· No membranes to replace
· Maintenance of the sensor is limited to wiping the sensor clean
· No special skills are required to change a sensor cap... no stretching membranes, no worrying about air bubbles, no waiting for membranes to relax
· No risk of membrane failures such as tearing
· No consumable anodes, membranes, or electrolyte to be maintained or replaced with every calibration
· Improved accuracy and stability gives users the best DO data
· The sensor includes an internal standard that provides a consistent reference after every
· measurement to maintain stable readings throughout the deployment
· Tests show that Hach LDO data is more accurate and consistent that even Winkler Titrations!
Other important notes about Hach LDO
· Hach is the world leader in LDO technology. The company has built and shipped thousands of LDO
· sensors for use in the environmental, wastewater, industrial, and laboratory markets.
· Hach LDO is designed, manufactured, and serviced by Hach. Hach has complete control over the printing
· process, the luminescent material, and the conversion algorithms. This also means that our customers can receive sales support directly from the source!
· Hach LDO is completely integrated into the Series 5 sondes. Therefore, the sensor can be brushed by
· our DS5X to remove any active fouling (eg, barnacles) that consume oxygen and would otherwise misrepresent the condition of the water.